The present invention relates to a novel method of applying silica coatings on electronic substrates. The novelty herein resides in the fact that silazane polymers are used as silica precursors.
Various methods for the application of ceramic coatings on electronic devices are known in the art. For instance, it is known to use gaseous precursors in a variety of vapor deposition processes to produce coatings of silica, silicon nitride, silicon oxynitride, silicon carbide and the like. These coatings are taught to be useful as protective and dielectric layers.
Similarly, the use of polymeric precursors for depositing ceramic coatings on electronic devices is also known in the art. For instance, Haluska et al. in U.S. Pat. Nos. 4,749,631 and 4,756,977 and the Accuglass.TM. product literature disclose silica coatings produced by applying solutions of silica precursors to the devices and then heating the coated devices to convert the precursors to silica. These references, however, do not disclose the use of polysilazanes as the silica precursors.
Finally, the use of polysilazanes for applying silicon and nitrogen containing ceramic coatings on electronic devices is also known in the art. For example, Haluska et al. in U.S. Pat. Nos. 4,756,977 and 4,826,733 teach forming ceramic coatings by applying coatings of silicon and nitrogen containing polymers such as polysilazanes on such devices and then heating the coated devices in an inert atmosphere. Since the coatings are heated in an inert atmosphere, the nitrogen is maintained in the coating and, thus, silica is not formed.
The present inventors have now discovered that silica coatings derived from silazane polymers can be applied on electronic substrates. Since the resultant coatings are thick, planar and defect free, they can be used as protective and dielectric layers.